1. Cellular Wireless Networks and Macro Base Stations
Many people use mobile stations, such as cell phones and personal digital assistants (PDAs), to communicate with cellular wireless networks. These mobile stations and networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless protocol such as Code Division Multiple Access (CDMA), perhaps in conformance with one or more industry specifications such as IS-95 and IS-2000. Wireless networks that operate according to these specifications are often referred to as “1×RTT networks” (or “1× networks” for short), which stands for “Single Carrier Radio Transmission Technology.” Another protocol that may be used is known as Evolution Data Optimized (EV-DO), perhaps in conformance with one or more industry specifications such as IS-856, Release 0 and IS-856, Revision A. Other protocols may be used as well, such as Global System for Mobile Communications (GSM), Time Division Multiple Access (TDMA), and/or any others.
These networks typically provide services such as voice, Short Message Service (SMS) messaging, and packet-data communication, among others, and typically include a plurality of base stations, each of which provide one or more coverage areas, such as cells and sectors (i.e., individual areas of a cell that allow the cell to carry more calls). When a mobile station is positioned in one of these coverage areas, it can communicate over the air interface with the base station, and in turn over one or more circuit-switched and/or packet-switched signaling and/or transport networks to which the base station provides access.
The base stations for these networks are typically not associated with any subscriber or small group of subscribers in particular; rather, they are placed in publicly-accessible locations and are used by the service provider's customers generally. These base stations collectively blanket cities, rural areas, etc. with coverage; as such, they are referred to generally and herein as “macro base stations,” and the network they collectively form—or to which they collectively belong—is referred to generally and herein as the “macro-network.”
Mobile stations and macro base stations conduct communication sessions (e.g. voice calls and data sessions) over a frequency known as a carrier, which may actually be a pair of frequencies, with the base station transmitting to the mobile station on one of the frequencies, and the mobile station transmitting to the base station on the other. This is known as frequency division duplex (FDD). The base-station-to-mobile-station link is known as the forward link, while the mobile-station-to-base-station link is known as the reverse link.
Furthermore, using a sector as an example of a coverage area, macro base stations may provide service in a given sector on one carrier, or on more than one. An instance of a particular carrier in a particular sector is referred to herein as a sector/carrier. In a typical CDMA system, using a configuration known as radio configuration 3 (RC3), a macro base station can, on a given sector/carrier, transmit forward-link data on a maximum of 64 distinct channels at any time, each corresponding to a unique 64-bit code known as a Walsh code. Of these channels, typically, 61 of them are available as traffic channels (for user data), while the other 3 are reserved for administrative channels known as the pilot, paging, and sync channels.
When a macro base station instructs a mobile station assigned to a given sector/carrier to use a particular traffic channel for a communication session, the macro base station does so by instructing the mobile station to tune to one of the 61 traffic channels on that sector/carrier. It is over that assigned traffic channel that the macro base station will transmit forward-link data to the mobile station during the ensuing communication session. And, in addition to that forward-link channel, the traffic channel also includes a corresponding Walsh-coded reverse-link channel, over which the mobile station transmits data to the macro base station.
2. Femtocell Base Stations
Many macro-network subscribers, including private consumers and small businesses, among others, in addition to having wireless service (which may include data service) for their mobile station(s), also have high-speed (a.k.a. “broadband”) Internet access through another communication channel. This other channel may be cable-modem service, digital-subscriber-line (DSL) service, satellite-based Internet service, and/or some other option.
In an exemplary arrangement, a user may have a cable modem connected (a) via coaxial cable to the cable provider's network and (b) via Ethernet cable to a wireless (e.g. IEEE 802.11 (WiFi)) router. That router may include one or more Ethernet ports to which computers or other devices may be connected, and may also include wireless-access-point functionality, providing a WiFi packet-data interface to laptop computers, digital video recorders (DVRs), appliances, and/or any other computing devices or their wireless network adapters.
To address gaps in macro-network coverage (e.g. poor in-building coverage) and for other reasons, macro-network service providers have recently begun offering consumers devices referred to herein as femtocell base stations, which may also be referred to as femtocells (femto base stations, femto base transceiver stations (BTSs)), picocells (pico base stations, pico BTSs), ubicells, microcells (micro base stations, micro BTSs), and perhaps by other names. Note that the aforementioned terms that end in “cell” may also be generally and herein used interchangeably with the coverage area provided by the respective devices.
A typical femtocell base station may be approximately the size of a desktop phone or WiFi access point, and is essentially a low-power, low-capacity, low-cost version of a macro base station. Thus, a typical femtocell base station will use a normal power outlet, perhaps with a transformer providing a DC power supply. The femtocell base station may have a wired (e.g. Ethernet) or wireless (e.g. WiFi) connection with the user's router, and would thus have connectivity to the Internet and/or one or more other packet-data networks via the user's broadband connection. A femtocell base station may establish a virtual-private-network (VPN) connection over the Internet with an entity (e.g. a VPN terminator) on the wireless-service provider's core network, and thereby be able to securely communicate with the VPN terminator and other entities on that core network and beyond.
The femtocell base station also has a wireless-communication (e.g. CDMA) interface that is compatible with the user's mobile station(s), such that the femtocell base station may act as a micro base station, providing coverage on the wireless-service provider's network via the user's Internet connection. Usually, a femtocell base station will provide service on a single RF carrier (or on a single carrier per technology, where multiple technologies (i.e. CDMA, EV-DO) are supported), and also transmit what is known as a pilot beacon, which includes administrative messages and parameters that mobile stations can use to connect with the femtocell base station. And femtocell base stations typically include a Global Positioning System (GPS) receiver for use in receiving and decoding GPS signals, for use in determination of location, as well as for use in synchronizing operations with other femtocell base stations and with the macro-network, based on timing information embedded in GPS signals. Typically, femtocell base stations have fairly comprehensive auto-configuration capabilities, such that they are largely “plug-and-play” to the user.
3. Licensed Frequency Spectrum
Various government agencies, such as the Federal Communications Commission (FCC) in the United States, regulate the use of radio spectrum. The regulation of radio spectrum may include licensing the radio spectrum to a limited number of entities. The regulation of radio spectrum may also include imposing penalties, such as imposing a monetary fine or revoking a license, to an unlicensed entity that interferes with the radio spectrum of a licensed entity.
A wireless service provider that operates a macro-network is typically the holder of a plurality of radio spectrum licenses that authorize the service provider to provide wireless service via its licensed radio spectrum. The licensed radio spectrum of a given wireless service provider may cover a distinct geographical area. If the given wireless service provider is found to interfere with licensed radio spectrum outside its distinct geographical area (e.g., by providing wireless service outside its distinct geographical area), the regulating government agency may penalize the given wireless service provider. Thus, wireless service providers strive to avoid interfering with radio spectrum outside the distinct geographical area where they are licensed to provide wireless service.